[llvm] [DebugInfo] Introduce DW_AT_LLVM_language_dialect (PR #194898)

[Matt Davis via llvm-commits]

enferex wrote:

Sorry for all the noise on the PR. I was updating my branch and caused all kinds of havoc on this PR, including adding a ton of other reviewers, which was not intentional.  I've reset my branch back to before that chaos.

I've made a few updates to the PR, including more testing, an updated warning, and more comments.  I agree with you both @dwblaikie and @echristo .  The string dialect makes sense as a way to explore this "dialect" idea; however, making it an enum seems more fool-proof than strings as a long term solution.  

https://github.com/llvm/llvm-project/pull/194898